Investigators haven't figured out what caused a crane to tip over Monday morning while crews were working on a chimney at the Rathskeller restaurant on East Michigan Street.

Three people suffered minor injuries when the 30-ton machine tipped over into the Athenaeum building, which also houses a YMCA branch. Two were taken to a local hospital for treatment.

Inspectors are working to assess the structural damage, but officials think the YMCA may be closed up to two weeks. Rathskeller managers expect the restaurant and its outdoor Biergarten to reopen Tuesday.

Both the YMCA and Rathskeller sustained water damage when their sprinkler systems went off. More than 150 occupants of the building were evacuated.

The crane was stretched 90 feet into the air when it tipped over behind the building. A second crane will be brought in to right the fallen machine.

The Athenaeum Building dates to the 1890s and was designed by the paternal grandfather of author Kurt Vonnegut.

Fox59 will have more at 4 p.m.

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The Associated Press contributed to this report.